Common Sharness test repo for all IPFS implemetations

[chriscool]

@diasdavid suggested creating a common Sharness repo that would host the Sharness test scripts for all the IPFS implementations.

Current Sharness tests require a number of go programs like go-sleep, go-timeout, hang-fds, ma-pipe-unidir, go-poll-endpoint (see https://github.com/ipfs/go-ipfs/blob/master/test/sharness/Rules.mk), so go must be available on the Docker image where the Sharness tests are run.

This is a current problem for js-ipfs (see ipfs/js-ipfs#522).

We could have js-ipfs and go-ipfs builds trigger Sharness tests in the common Sharness repo to fix that problem.

But then one problem is that it looks like Travis doesn't have and doesn't plan to add the "dependent build" feature:

travis-ci/travis-ci#249

So we would need another way to trigger Sharness builds when the js-ipfs and go-ipfs repo are updated.

[Kubuxu]

We could have a docker image with tooling in it (and the suite) and then you would volume mount your implementation with ipfs "binary". We will be also moving away from Travis and expanding our Jenkins so we have a lot more possibility.

[chriscool]

Ok to move to Jenkins.
Otherwise the following could be useful with Travis:
https://stackoverflow.com/questions/35165970/set-up-upstream-project-in-travis-ci
http://eng.rightscale.com/2015/04/27/dependent-builds-in-travis.html